Hi askdjasd,
I'm only somewhat involved in the volunteer dive program at the Aquarium as my department (Tropical Waters) uses them for diving in the shark exhibit, Indo-Pacific reef and under very special circumstances, the giant fishes exhibit. Normally, the Aquarium asks for a bit of a committment - somewhat regular attendance in exchange for some diver education and a chance to dive in some pretty special places (exhibits). It's usually a lot of hard work using either elbow grease or powered scrubbers and vis really varies - from unlimited (at least to the other wall...) to down-right "Lake Erie of the early 80's" - depending on exhibit and how much sun rainy-Vancouver has received.
When I was running the volunteer diving program in the early 90's I offered instruction and practice with gear configuration, finning techniques and buoyancy skills - all useful skills and exercises for exhibit diving.
Anyway, we'd really have a tough time maintaining the exhibits with only staff divers so we value our volunteers very much. I hope you get as much from the experience as the Aquarium does!
Lee Newman
Curator of Tropical Waters
Vancouver Aquarium